BURLINGTON — Less than a month after raising the estimated cost of Phase 1 of a natural gas pipeline project by 40 percent, Vermont Gas has announced that the Phase 2 cost is going up as well.

Phase 1, from Chittenden County to Middlebury, is under construction now. The company hopes to follow that up with Phase 2 from Middlebury to the International Paper plant in Ticonderoga, N.Y., with an extension under Lake Champlain.

The paper company is paying most of the cost of Phase 2, and that applies to the $10 million cost increase as well.

Vermont Gas also plans a third phase to extend the pipeline to Rutland.